After the Class SP45 has proven itself as the first express
locomotive in Poland, the Polish Federal Railways decided to
procure a more powerful version to be used in heavy high-class
passenger train service. Because of its reliability, the
constructors fell back on the FIAT engine of the SP45 and increased
its power to 2250 HP. Among the innovative features of the latest
PKP diesel locomotive were the electric train heating and the
optimised form of the driver’s cabin and the car-body with ribbed
side walls.
Prototype SU46-001 is rolled out.
Second prototype SU46-002 is delivered.
After recognising and eliminating some teething problems with the
prototype locomotives SU46-001 and SU46-002, the Poznan locomotive
manufacturer Cegielski delivered 50 more SU46 locos between 1976
and 1977 with a total power of 1654 KW and a high speed of 120
km/h.
First SU46s in PKP service were used mainly with heavy express
passenger trains, for which SP45s had been too weak. Modest
deliveries of heavy passenger diesel locomotives never allowed for
complete elimination of steam traction, which remained in regular
service in Poland much longer than in other European countries. As
electrification progressed, steam finally disappeared and later
many SU46 were relegated to secondary lines; for a number of years
a SU46 with just one or two coaches was not an uncommon view.
Despite their designation, which implies a universal locomotive,
they were initially seldom used with freight trains; later,
however, they often appeared on the Węgliniec-Horka line between
Poland and Germany, as Germans were reluctant to let ST43
locomotives in. With gradual introduction of diesel railcars, which
offer much better economy on secondary lines, more and more SU46s
are being shifted to freight traffic.
The program stopped as the manufacturer focused on building a new
two-unit heavy electric freight locomotive, based on EU07 and
delivered for the first time in 1977 as ET41. So the PKP continued
to import M62 diesel locomotives from the Soviet Union (designated
ST44 in Poland) despite the lack of carriage heating devices, an
increased fuel consumption and huge damages to the railway
tracks.
This immediately resulted in lack of spare parts for existing SU46
machines. Problems with diesel engines were particularly acute, as
production of the W2112SSF was also halted. As a result,
availability of SP45s and SU46s in PKP service deteriorated
rapidly. Many local passenger trains had to be hauled by steam
locomotives or diesel freighters with heating cars.
The Ministry of Transport wishes to order 267 slightly modified
SU46s. Deep economic crisis, however, turned these plans into a
mere wishful thinking. It proved impossible to maintain
simultaneous production of electric and diesel locomotives and, as
the former were given priority, only two more SU46s were built in
December 1985. These machines – SU46-53 and SU46-54 – differed from
their predecessors only in minor details and factory designation
remained unchanged (externally they could be distinguished by
different louvers on side walls).
The 2 prototypes were withdrawn in 1990 (both were later scrapped)
and several more were written off in late 1990s, when almost 100
heavy passenger diesels were declared surplus by PKP (in fact, most
of them were unserviceable examples, awaiting spares, often for
several years).
PKP is split into several companies and SU46 locomotives went to
PKP Cargo.
PKP Cargo still has 36 SU46 locomotives. From time to time some of
them are hired to be used on passenger InterCity trains.
SU46-049 is rebuilt by PESA and fitted with the MTU 12V4000R43L
12-cylinder diesel engine, d2500 hp. Old traction engines were
retained. Car heating equipment was removed and, apart from many
minor improvements, cab air-conditioning system and new rectangular
headlights were fitted. This "new" locomotive is designated as
ST46.